The subject matter described herein relates generally to power systems and, more particularly, to galvanic isolation of gate-controlled devices used in power systems.
In some known renewable energy power systems, direct current (DC) electrical power is generated from at least one renewable energy source or generated alternating current (AC) electrical power is inverted to DC electrical power and then converted back to AC. Such renewable energy sources may include wind, solar, geothermal, hydro, biomass, and/or any other renewable energy source. To properly couple such power systems to an electrical grid, the DC electrical power must be converted to AC. At least some known power systems use a power converter to convert DC power to AC power. In some instances, the converter can be a parallel converter.
In many instances, power converters use gate-controlled devices such as, for example, insulated gate bipolar transistors (IGBT), injection-enhanced gate transistors (IEGT), silicon controlled rectifiers (SCR), gate turn off (GTO) thyristors, gate controlled thyristors (GCT), integrated gate commutated thyristors (IGCT), metal-oxide semiconductor field effect transistor (MOSFET), and the like. Generally, control signals to these gate-controlled devices and signals transmitted by the gate-controlled devices are required to be isolated from the electrical system that they are a part of and/or from electromagnetic interference in order to provide accurate signaling. Galvanic isolation is a term that describes a method of electrical isolation between sections of electrical systems. Gate-controlled devices ordinarily utilize a transformer as the galvanic isolation method to deliver the power to the gate drive circuitry of the gate-controlled device, and gate-controlled devices ordinarily utilize a signal isolated by light (such as fiber optic or optocoupler) as the galvanic isolation method to deliver the control signals to/from the gate drive circuitry. The galvanic isolation of the control signals utilizing fiber optic or optocoupler is expensive, and has limitations in terms of a tradeoff of the cost vs. performance analysis. For example an optocoupler usually has a voltage limitation making it impractical for high voltage isolation, and in contrast, fiber optics are capable of high voltage isolation but at a higher cost.
Described herein are embodiments of methods, apparatus and systems for the galvanic isolation of the control signals to and from a gate-controlled device that overcome challenges in the art, some of which are described above.